TITAN ROCKET

any of a series of U.S. rockets that were originally developed as intercontinental ballistic missiles (ICBMs) but were also used as space launch vehicles. The Titan I, the first in the series, was built by the Martin Company (now the Lockheed Martin Corporation) for the U.S. Air Force in the late 1950s. A two-staged ICBM fueled by kerosene and liquid oxygen, it was designed to deliver a four-megaton nuclear warhead more than 5,000 miles (8,000 km) to targets in the Soviet Union. Between 1962 and 1965 several squadrons of Titan Is were operational at air force bases in Western and Pacific Coast states. The missiles were stored underground in reinforced-concrete silos but had to be raised to ground level for launch and required a minimum of 15 to 20 minutes for fueling. By 1965 the Titan I had been replaced by the Titan II, a much larger ICBM (approximately 100 feet long) that could be launched directly from its silo and was fueled by internally stored hypergolic fuels (self-igniting liquids such as hydrazine and nitrogen tetroxide). Tipped with a warhead of nine megatons' force (the most powerful nuclear explosive ever mounted on a U.S. delivery vehicle), Titan II, stationed at bases in the central and western United States, was the principal weapon in the land-based U.S. nuclear arsenal until it was replaced by more accurate solid-fueled ICBMs such as the Minuteman. The last Titan IIs were deactivated between 1982 and 1987. The Titan II was also used by the National Aeronautics and Space Administration (NASA) as the launcher for the Gemini manned spacecraft during the 1960s. After its deactivation as an ICBM, it was modified by Lockheed Martin to launch satellites for military and civilian use. The Titan III was a series of space launchers based on the Titan II. In order to acquire greater thrust, most of the rockets employed two strap-on boosters burning solid propellants. A variety of upper stages, such as Agena or Centaur, were mounted atop the second stage in cases when further maneuverability or escape from Earth orbit were required. The most successful vehicles in the series were the 160-foot Titan III-E/Centaur combination, which launched the Viking, Voyager, and Helios space probes during the 1970s. The Titan IV, developed from the Titan III in the late 1980s, was built with larger and more powerful engines in order to lift heavy payloads such as those carried by the Space Shuttle. Boosted by two solid-propellant strap-ons and often combined with an upper stage such as Centaur, it became the largest expendable launch vehicle (approaching 200 feet) employed in the United States. The Titan IV series lifted a number of civilian and military satellites into space.